Can a married fornicator be purified of his sin through repentance, or will Allah purify him with the fire of Hell on the Day of Judgment, and does he owe any rights to the husband whose honor he violated, and is it permissible for the female fornicator to ask for his forgiveness without informing him of her sin?

The married fornicator, like other sinners, if he repents with a sincere repentance that fulfills its conditions—remorse, cessation [of the sin], determination not to return [to it], sincerity, and that the repentance occurs before it is too late—then Allah will accept his repentance and erase his sin. The Hadith has indicated that whoever repents from fornication before the Hadd (prescribed punishment) is carried out on him, Allah accepts his repentance. It is not a condition for the fornicator to seek absolution from the husband of the woman with whom he committed fornication; because this would create discord and evil. However, it is commendable to do good to the husband of the woman with whom he committed fornication by supplicating for him, seeking forgiveness for him, and giving charity on his behalf.